1. Field of the Invention
The present invention relates to an image recording apparatus.
2. Description of the Related Art
Video cameras that record captured picture signals on magnetic tape are well known. In recent years, a video camera has emerged that codes a captured picture signal in the Moving Picture Experts Group (MPEG) standard and records it.
Generally, video cameras of this type capture and record picture signals of 60 fields per second under the National Television System Committee (NTSC) system. Video cameras have also appeared that have a capability of capturing a picture signal of 24 frames per second, like a movie, as well as a picture signal of 60 fields per second, converting it into a picture signal of 60 frames per second, and recording the converted signals.
As a method of converting a film source like a movie into an interlaced video signal, a technique of 2-3 pull down is widely used. A film runs at 24 frames per second, whereas a video runs at 30 frames (60 fields) per second. Therefore, the number of fields is converted. More specifically, as shown in FIG. 1, a redundant field (hereinafter referred to as a repeat field) is interposed every other frame to convert the number of fields.
Since a video signal subjected to 2-3 pull down has a repeat field every other frame, a frame that starts at a top field and a frame that starts at a bottom field are alternated every two frames.
On the other hand, when a normal interlaced video signal of 60 fields is recorded under the MPEG standard, since two fields counting from a top field are generally coded as one frame, all frames start at their top fields.
As shown in FIG. 2, with a video camera, in the case where MPEG data that have been coded using 2-3 pull down and MPEG data that have been coded from a normal 60-field picture signal are subjected to connection recording on tape, a field alternation error of consecutive top fields may occurs depending on connected fields, and this may cause unsmooth playback.
One approach to this problem is discussed in Japanese Patent Laid-Open No. 9-121360. In this patent document, compression coding is performed in units of fields, and a field to start cording and a field to stop coding are defined, thereby enabling connection editing and recording of streams.
However, as shown in FIG. 3, because an apparatus disclosed in the patent document defines the sequence of top and bottom fields in coding order, connection editing and recording to MPEG data that have been coded using 2-3 pull down cannot be carried out appropriately.
At a point of connection editing and recording, a field gap occurs.
Additionally, as shown in FIG. 4, because a repeat field is not defined, a decoding time period which is not required normally is required at a connection point. At an area 401, although a normal 60-field interlaced stream, a decoding time period of 3 fields is required. This kind of streams is prone to causing various problems in coding and decoding stages.
Therefore, such connection recording can be disabled. However, for the apparatus disclosed in Japanese Patent Laid-Open No. 9-121360, it is difficult to support various types of formats and solve problems that may occur in coding and decoding.